<template>
  <div class="spec-preview">
    <img :src="skuImageList[defaultIndex]?.imgUrl" />
    <div class="event" @mousemove="mousemove"></div>
    <div class="big">
      <img :src="skuImageList[defaultIndex]?.imgUrl" ref="bigImg" />
    </div>
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
export default {
  name: "Zoom",
  props: ["skuImageList"],
  mounted() {
    // 接收传递的ImageList传递的index参数
    this.$bus.$on("changeDefaultIndex", (value) => {
      return (this.defaultIndex = value);
    });
  },
  data() {
    return {
      defaultIndex: 0,
    };
  },
  methods: {
    mousemove(e) {
      // 鼠标到外层边缘的位置
      const mouseToOut = {
        left: e.offsetX,
        top: e.offsetY,
      };

      // 计算蒙版的位置
      const maskLocation = {
        x: mouseToOut.left - this.$refs.mask.offsetWidth / 2,
        y: mouseToOut.top - this.$refs.mask.offsetHeight / 2,
      };

      // 处理临界值
      if (maskLocation.x < 0) {
        maskLocation.x = 0;
      } else if (
        maskLocation.x >=
        e.target.clientWidth - this.$refs.mask.offsetWidth
      ) {
        maskLocation.x = e.target.clientWidth - this.$refs.mask.offsetWidth;
      }

      if (maskLocation.y < 0) {
        maskLocation.y = 0;
      } else if (
        maskLocation.y >=
        e.target.clientHeight - this.$refs.mask.offsetHeight
      ) {
        maskLocation.y = e.target.clientHeight - this.$refs.mask.offsetHeight;
      }

      // 赋值
      this.$refs.mask.style.left = maskLocation.x + "px";
      this.$refs.mask.style.top = maskLocation.y + "px";

      // 控制大图位移
      this.$refs.bigImg.style.left = -2 * maskLocation.x + "px";
      this.$refs.bigImg.style.top = -2 * maskLocation.y + "px";
    },
  },
};
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>